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Homework Help: Enthalpy of Ionization

  1. Mar 19, 2009 #1
    1. The problem statement, all variables and given/known data

    Find the enthalpy of ionization of the weak acid, ΔH3

    H3O+ + OH- <-> 2H2O.................ΔH1
    HA + OH- + H2O <-> A- + 2H2O....ΔH2
    HA + H2O <-> H3O+ A-...............ΔH3

    3. The attempt at a solution

    I won't show it here but I've found ΔH1 to be -52.33 kJ/mol and ΔH2 to be -5.21 kJ/mol. I don't know how to get the third enthalpy though, I know you'd use Hess' law but I don't really understand what to do here.
  2. jcsd
  3. Mar 20, 2009 #2


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    Staff: Mentor

    Obviusly you have to start with the second reaction, as it has HA and A- in correct places. Then use the first reaction to get rid of OH- on the LHS and H2O on the RHS.
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